For regular PSs I use MS, for anything requiring CC deposits (like CP Dinner Pkg) you need to call the WDW DINE. ALso for hard to get PSs, like Cinderella Breakfasts, call Dining.
I have always used MS for my PS and they are great. I did call WDWdine for CP package. I think I would use regular WDWdinw for any princess stuff, but luckily I have a 14 year od DS!
Connears
I usually call the regular dining line, and use MS only when I know the dining line is busy... like this Thanksgiving. People were on hold with dining for up to 3 hours... I got through to MS immediately.